Light emitting devices, such as light emitting diodes (LEDs), may be used in packages or devices for providing white light (e.g., perceived as being white or near-white), and are developing as replacements for incandescent, fluorescent, and metal halide light products. In general, LED packages are either ceramic based with copper (Cu) traces or polymer-based with a Cu leadframe, where one or more LEDs electrically communicate with the Cu. For packages using a Cu leadframe, the leadframe needs to have a certain thickness for stability during processing and structural integrity to withstand injection molding forces. In conventional ceramic based packages, the Cu traces used are approximately 50 microns (μm) or greater in thickness. According to conventional wisdom, thick Cu traces are necessary to spread heat and assist with heat flow through the ceramic and away from the LED.
A prior art LED package, generally designated 10 is illustrated in FIG. 1. LED package 10 comprises a ceramic-based submount 12 over which one or more layers of electrically conductive material generally designated 14 can be deposited or otherwise attached. Conventional ceramic-based submounts 12 include, for example, aluminum oxide (Al2O3). Conductive material 14 can comprise conventional Cu traces which have been electro-plated or otherwise deposited, over submount 12 and electrically isolated. In one aspect, a single layer of Cu can be deposited over submount 12 and then subsequently etched, thereby forming one or more electrically isolated traces 18 and 20. Conductive material 14 can comprise a Cu layer having a thickness of approximately 50 μm or greater. At least one LED 16 can mount to a first trace 18 and electrically connect to a second trace 20 via wirebonding using an electrically conductive wire 22. First and second traces 18 and 20, respectively, can receive electrical signal or current from one or more electrical contacts 24 and 26, respectively. Electrical contacts 24 and 26 can receive an electrical signal from an external source, for example, an electrical circuit. The electrical current can then be passed from first and second traces 18 and 20 into LED 16, thereby illuminating the LED when the electrical energy is converted into light. LED package 10 can further comprise a lens 28.
As known in the art, a gap 30 can be etched or otherwise formed between first and second traces 18 and 20, respectively, and typically results in a gap 30 having approximately a 1:1 aspect ratio between trace thickness and gap width. That is, Cu that is approximately 50 μm in thickness will result in a gap 30 having a depth D of approximately 50 μm and a width W of approximately 50 μm. Thicker gaps 30 can require a larger submount surface area, which is generally undesirable. The size of such a gap can also be disadvantageous as it provides an undesirable larger space for light from the LED to pass into the gap thereby reducing or limiting light output. The relatively high cost and processing time associated with manufacturing devices and packages using Cu traces that are approximately 50 μm or greater in thickness is also undesirable. However, as noted above and according to conventional wisdom, thick Cu traces are necessary to spread heat and assist with heat flow through the ceramic substrate and away from the LED. Despite conventional wisdom and manufacturing difficulties, the subject matter herein advantageously incorporated thinner Cu traces which led to unexpected results of no reduction in LED, device, and/or package performance over time when Cu trace thickness is minimized.
Despite availability of various LED devices and packages in the marketplace, a need remains for improved packages that can be manufactured at a lower cost in less amount of time without compromising LED performance. LED packages and methods disclosed herein advantageously use thin metal components, have low thermal resistance, and have improved light output performance which thereby improves device reliability. Advantages of using thin metal components can include, for example, more efficient LED designs, routing of electrical signal under parts (as opposed to around parts), a reduction in encapsulant, and a simplified, less-expensive manufacturing process (i.e., by eliminating Cu and electroplating processes).